The mountain pass at Lazikou (Gansu province) was captured on 16 September 1935. After direct attacks on the Nationalist troops had failed, Mao ordered soldiers with mountaineering skills to climb the peak above a blockhouse the Nationalists had built, and throw grenades. This tactic succeeded. The mountaineers can be seen climbing on the right of the image, the burning blockhouse is high in the center.
Nr. 7 of the poster set An arduous journey.
This is a print from the tenth edition (January 1965).